Biomedical subjects

A Ranasinghe

Publications and source records attributed to A Ranasinghe.

22 records · Page 2Linked to original sources

PubMed1993

A rapid screening method for artemisinin and its congeners using ms/ms: search for new analogues in Artemisia annua.

A rapid screening method based on tandem mass spectrometry (ms/ms) is described for artemisinin-related compounds present in complex matrices. These compounds produce abundant ammonium adducts, [M + NH4]+, using ammonia desorption chemical ionization (dci), and dissociation of the mass-selected adducts yields the protonated molecules, [M + H]+, which subsequently eliminate characteristic neutral molecules (H2O, CO, HCO2H, HOAc). Neutral loss ms/ms scans which are selective for different elimination reactions were used in order to screen for groups of related analogues present in a crude hexane extract of Artemisia annua. Comparison of ms/ms product spectra of known Artemisia compounds with those of the new analogues provided information on the functional groups and the molecular weights of the new compounds present in the plant, and tentative structures are suggested.

Antimalarials↗

PubMed1985

An organ culture model for examining epidermal desquamation.

The use of organ cultures of mouse ear skin for examining mechanisms of stratum corneum shedding has been investigated. The formation and loss of stratum corneum cells was assessed by electron microscopic autoradiography and from counts of stratum corneum cell layers taken from sections of plastic-embedded specimens. Using media supplemented with cortisone, there was a linear accumulation of stratum corneum cell layers and the rate of epidermal cell formation corresponded approximately to that in vivo. Cells that accumulated at the stratum corneum surface were loose and could consistently be removed by treatment with detergent and ultrasonication indicating the persistence of shedding mechanisms in vitro.

Animals↗

PubMedDate not supplied

Synthesis of [4,5,6,8-(13)C4]guanine, a reagent for the production of internal standards of guanyl DNA adducts.

Using readily available labeled compounds, [4,5,6,8-(13)C4]guanine was synthesized in high overall yield. Intermediates as well as the final product were characterized by 1H NMR, 13C NMR, and high resolution mass spectrometry. The labeled guanine was used to generate [13C4]-labeled analogs of the guanine adducts, N2,3-ethenoguanine and 7-(2-hydroxyethyl)guanine. The application of such adducts in isotope dilution mass spectrometry was illustrated with DNA samples from rats exposed to two different mutagenic compounds, vinyl chloride and ethylene oxide.

Animals↗

PubMedDate not supplied

Some oral carcinomas from Sri Lankan betel/tobacco chewers overexpress p53 oncoprotein but lack mutations in exons 5-9.

We reported a low prevalence (11%) of p53 expression detected by immunohistochemistry in oral squamous cell carcinomas associated with betel/tobacco chewing Sri Lankans (23). Five neoplasms which over-expressed p53 protein were used in the present study of mutations. Despite extensive sequence analysis no mutations were detected in exons 5 through 9 of the p53 gene in all the DNA samples of these neoplasms. Thus, over-expression of p53 is not necessarily synonymous with mutations in the exons studied, although mutations of this gene have been reported in oral and head and neck cancer from Japan and USA. The absence of mutations in betel/tobacco related carcinomas in this population may derive from differences in aetiology, carcinogen metabolism and susceptibility, DNA repair mechanisms and/or genetic predisposition.

Areca↗